1. Technical Field
The present invention relates to an exposure equipment adapted for use in the manufacture of semiconductor devices. More particularly, the invention relates to exposure equipment and related methods of operation in which an optical system is positioned so as to minimize imaging errors.
This application claims priority from Korean Patent Application No. 2004-75669 filed Sep. 21, 2004, the disclosure of which is hereby incorporated by reference in its entirety.
2. Discussion of the Related Art
The manufacture of semiconductor devices is a long and complicated process. It generally starts with the fabrication of defect-free silicon wafer. Before actually forming circuits and elements on the wafer it must be carefully machined, polished and cleaned. Thereafter, a multiplicity of specific processes are sequentially applied to the wafer in order to form the multi-layer circuits and elements that constitute a contemporary semiconductor device. Such processes are conventional in nature and well understood. They include, as ready examples, processes related to photolithography, etching, thin film deposition, diffusion, etc.
Photolithography is a well known process that comes in a variety of types and capabilities. Generally speaking, however, a photolithography process transfers geometric shapes defined by a mask onto the surface of the silicon wafer being processed. The steps typically involved in a photolithographic process include; wafer cleaning, barrier layer formation, photoresist application, soft baking, mask alignment, exposure and development, and hard baking.
The photolithography exposure is a process of transferring a circuit pattern formed on a reticle onto the surface of a wafer, wherein the wafer has a photosensitive film applied thereon. The circuit pattern is transferred through an optical system which optically reduces it during transfer. The photolithography exposure process is typically implemented using exposure equipment, such as a scanner.
Given the minute detail involved in most contemporary circuit patterns, it is very important to continuously inspect and, if necessary, correct the physical position of the exposure equipment in relation to the wafer. Highly accurate positioning of the exposure equipment is required in order for the circuit pattern formed on the reticle to be precisely transferred onto each targeted portion of the wafer. Each circuit pattern transfer is sometimes referred to as a “shot.”
This delicate positioning process is further complicated by the speed at which contemporary semiconductor fabrication lines operate. In practical application, the exposure equipment moves very quickly between respective shot positions. Unfortunately, mechanical vibration is often an undesired byproduct of the rapid positioning of the exposure equipment. Unless corrected or compensated for, a transfer image defect referred to as a “dynamic performance error” may arise from this vibration. Accordingly, high-precision inspection and compensation operations are indispensably required.
Several conventional methods have been proposed to reduce the risk of dynamic performance error. For example, one conventional method of reducing dynamic performance error shields the optical system from vibration by maintaining a vacuum state within certain interior portions of the exposure equipment. Another conventional method of reducing dynamic performance error compensates for such errors at the reticle stage of the process. However, these conventional methods only partially eliminate the dynamic performance error, and the resulting transfer image defect is only partially remediated.
Residual transfer image defects pose an increasingly unacceptable risk to the accurate fabrication of semiconductor devices. For example, the width of a circuit line in contemporary semiconductor devices may be as small as only 110 nm. Conventional methods of reducing transfer image defects are not adequate in the context of such highly precise circuit dimensions and tolerances. Consequently, an improved photolithography method having a better transfer image defect remedy is required.